The term "fastener assembly," such as a blind fastener or rivet, describes a fastener body comprising a head and a hollow deformable sleeve surrounding a stem having an enlarged head and a stem pull portion extending beyond the sleeve. The stem pull portion is pulled and eventually broken away from the fastener assembly by the tool after the fastener is set in a workpiece. The deformable sleeve locks the fastener in place.
In one method of automatically installing a blind fastener into a workpiece, a fastener assembly is transmitted from a fastener feeder to a fastener receive and place unit, which will take the received fastener and load it into the nosepiece of the fastener-setting tool. The receive and place unit is then moved out of the way, and the tool installs and sets the fastener in the workpiece. The cycle is repeated as needed.
The objective of an automatic fastener loading apparatus is to load a fastener into the fastener-setting tool as quickly as possible with the least amount of error. In view of the enormous number of fasteners used, even small improvements in the installation process can be very valuable.
Some devices used to load fasteners have employed a method of bringing the fastener close to but not touching the nosepiece of the tool and then pneumatically blowing the fastener into the nosepiece of the tool. This method of utilizing a positive burst of air led to may errors due to the fact that the fastener had to travel through the air before entering the tool.
This inaccuracy was compounded by the prior method of aligning the fastener to the tool. The prior devices held the fasteners in channels where they would in turn be shot into the tool. Alignment of a fastener by merely placing it in a channel with no other guiding means proved faulty.
Thus, to overcome this problem, prior devices have employed grippers to grip the fastener to aid the insertion into the nosepiece of the fastener-setting tool.
Prior devices utilized grippers in two different methods but both were still flawed. One type of gripper gripped the sleeve portion of the fastener, but since the stem pull portion, which is the part of the fastener which is inserted into the tool is still unguided, the accuracy of the loading method was low. This was especially apparent, since many fastener stems are not completely straight, and instead tend to have a slight natural curvature. Thus, although the sleeve may have been aligned with the nosepiece of the tool, it did not necessarily mean that the stem was aligned also.
A second type of device utilized fingers or jaws that appear like grippers but did not actually grip the stem pull portion of the fastener. Instead, the grippers utilized in these devices served mainly as a channel for guiding the fasteners into the nosepiece of the tool. The load cycle times for both these types of devices were relatively slow.
The accuracy of loading a fastener is especially important when dealing with staking tools which displace the material of the fastener body head or stem when setting the fastener. The difference between the diameter of the opening of the bore of the nosepiece of a staking tool and the diameter of the stem pull portion of a fastener is so small that minor misalignments can prevent the stem from entering the tool.
Therefore, there appears to be a need for a device to fulfill the objective of automatically loading a fastener assembly into the nosepiece of a fastener-setting tool as quickly as possible and as accurately as possible to ensure efficient loading.